The present invention concerns a timepiece including a clockwork movement, provided with an analogue display and at least one wheel and pinion fixed in rotation to a rotating indicator or display means of said analogue display, and a device for detecting, at least one reference angular position of said wheel and pinion, this detection device including a magnetic or capacitive sensor.
More particularly, the invention concerns a device for detecting at least one reference angular position of a toothed wheel of the gear train of a clockwork movement.
Those skilled in the art know optical devices for detecting at least one reference angular wheel position belonging to a gear train of a clockwork movement. All these optical detection devices are relatively complex. They require a light source and a light receiver at a distance from said source. The mounting operations of an optical detection device are often difficult given the precise adjustment necessary between the light source, the receiver and the wheel or wheels associated with this device. Within the scope of the present invention, it is therefore proposed to avoid any optical system for detecting the position of a wheel in a clockwork movement.
A system for detecting the position of coaxial wheels respectively associated with coaxial hands of a clockwork movement is known from the English abstract of International Patent Application No. WO 97/45705 (corresponding to U.S. Pat. No. 6,038,523--Akahane et al). On each solid or full toothed wheel are arranged several discrete portions of a hard thin magnetic film which define an identification pattern for a contactless magnetic sensor. Each of the wheels whose the angular position is able to be detected is associated with its own magnetic sensor. The amplitude of the signal detected by these magnetic sensors varies according to whether they are situated in front of segment of magnetic material or not, as is shown in FIGS. 3 and 4 of this International Patent Application. The detection system proposed in this document is disadvantageous because each wheel associated with a magnetic sensor has to be provided with distinct segments or portions of a solid film made of magnetic material arranged on one face of the toothed wheel. The manufacturing cost of the wheels is thus increased and the arrangement of the identification pattern is provided on a solid or full plate of the toothed wheel, which can be inconvenient for the working of the clockwork movement. The plates of the wheels are thus formed of at least two different materials, namely the material forming the base of the plate of the wheel and the magnetic material arranged at the surface of the base.